Conventionally, ink cartridges including ink, ink jet heads for discharging ink onto a sheet of recording paper and recording apparatuses have been known. In a known recording apparatus, its members, such as an ink cartridge, a tube through which ink is introduced to an ink jet head, and an adhesive agent used in the ink jet head, with which ink comes in contact are formed of resin, rubber, or like materials, in general.
In order to improve reliability and workability, a thermal stabilizer, an auxiliary stabilizer, a plasticizer, an antioxidant, a light stabilizer, a lubricating additive, or the like are added to resin, rubber, or like materials. Thermal stabilizers include metal soap types, lead containing types, and organic tin containing types. For example, Ba/Zn containing metal soap, lead stearate, organic monomethyltin or the like is used as a thermal stabilizer. Auxiliary stabilizers includes phosphite types, epoxy compound types, and β-diketone types. For example, trialkylphosphite, epoxy soybean oil, acetylacetone or the like is used as an auxiliary stabilizer. Plasticizers include aliphatic dibasic acid ester types, chlorinated paraffin types, polyester types, and epoxy types. For example, dibutyl phthalate, 2-etylhexyl adipate, chlorinated paraffin (chlorinated rate: 50%), epoxy soybean oil or the like is used as a plasticizer. Antioxidants includes phenol types, sulfur types and phosphorus acid types. For example, 2,6-di-t-butyl-4-methylphenol, dilauryl-3,3′-thiodipropionate, and trisnonylphenylphosphine is used as an antioxidant. As for light stabilizers, a UV sorbent can be used as a light stabilizer, and there are also hindered amine type light stabilizers. UV sorbents includes benzotriazole types and benzophenone types. For example, 2-(2′hydroxy-5′-methylphenyl) benzotriazole, 2,4-dihydroxybenzophenone or the like is used. Hindered amine type light stabilizers include, e.g., bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate. Lubricating additives include hydrocarbon types, fatty acid types, aliphatic alcohol types, aliphatic amide types, metal soap types and ester types. For example, alkylnaphthene hydrocarbon, stearic acid, stearyl alcohol, stearic acid amide, calcium stearate, butyl stearate or the like is used as a lubricating additive. Basically, it is difficult to maintain desired properties of resin, rubber or like materials unless such additives as the above-described ones are added thereto.
As for adhesive agents, which are acrylic resin, epoxy resin, silicon resin and the like, additives are also added for the purpose of attaining thermal stability, oxidation resistance, light stability, chemical resistance or the like, as in the same manner for the above-described resin, rubber or like materials.
Meanwhile, as ink for use in ink jet recording, ink containing a water-soluble dye as a colorant, a humectant, a penetrant and water is well known. It has been proposed that water-resistivity of an image formed on a recording medium is improved by making ink contain as a water-resistant agent a water-soluble substance such as a hydrolyzable silane compound which undergoes condensation polymerization even without water (Japanese Unexamined Patent Publication No. 11-293167, Japanese Unexamined Patent Publication No. 10-212439). In the ink, when an ink droplet is attached to the recording medium and then the water of the ink droplet evaporates or permeates into the recording medium, condensation polymerization of the water-soluble substance occurs. The condensation-polymerized water-soluble substance forms so-called “network” (a network structure) around molecules of a dye. Therefore, even though the image on the recording medium is wet with water, the dye molecules hardly go out of the network and thus hardly are eluted into the water. As a result, the water-resistivity of the image is improved.
However, in the conventional recording apparatus, ink comes in contact with members such as an ink cartridge formed of resin, rubber or like materials, and the ink then flows. This may cause elution of elements of the members into the ink due to temperature changes or changes thereof with passage of time. In such a case, there arises a problem in which eluted elements react with elements of the ink to form an impurity in the ink or to change properties of the ink.
In view of the above-described problems, the present invention has been devised and it is therefore an object of the present invention to specify the content of an additive added to a material for parts of an ink jet recording head, an ink cartridge, and a recording apparatus with which ink comes in contact and thereby to prevent properties of ink from changing.